The present disclosure relates generally to superconductive wire, methods of manufacture, and uses thereof in electronic components.
Typical superconductive (SC) rotating machines such as electrical motors and generators comprise a SC field coil and non-superconductive armature windings located, for example, on a stationary stator. When supplied a voltage, the field coil generates a magnetic field coupling the field coil and the armature windings. The magnitude of the coupling magnetic field is determined by the amount of current passed through the field coil and to a lesser extent by the armature reaction current from the load. The magnetic stress within the machine translates to torque resulting in rotation of the rotor. The higher the magnetic field, the greater the torque per rotation for a given circumference of armature windings and air gap surface area. Although the armature windings can also be superconductive, they are usually formed of non-SC material such as copper.
In established commercial superconductive (SC) wires, such as NbTi or Nb3Sn, the current carrying capacity is a function of the critical current Ic, the current where the material has a phase transition from a superconductive phase to a non-superconductive phase. Ic is a decreasing function of temperature T and magnetic field H. These SC wires also differ in price and manufacturing cost; for example, NbTi has a lower price and manufacturing cost, but also lower Ic than Nb3Sn. Superconductors also have a transition from the superconductive to non-superconductive phase at a transition temperature Tc and a critical field Hc, and it follows that they must be operated below this temperature and field.
In SC field coils, such as those used in SC electric motors and generators, the magnetic field H varies with location on the field coil, usually being higher at the inner parts of the coil, such as the inner surface or bore of a solenoid. Herein, the inner part of the field coil is referred to as the high-field region and the outer part of the coil, such as the outer surface of a solenoid, is referred to as the low-field region. One drawback of SC materials used to manufacture field coils is that some are more tolerant of the magnetic field than others. Less tolerant materials also tolerate lower current, which translates to weaker magnetic field strengths and less torque per given weight of SC material.
An ongoing need in superconductive rotating motors is reduction in the size and weight of the machines; that is, increasing the torque density for a given circumference of the field coil and armature windings. The practical benefits from miniaturization through more field tolerant electrical components in these and other machines include lower manufacturing costs, among others. This disclosure addresses the need for more field tolerant components.